Method for structuring endless belts for presses

ABSTRACT

The invention relates to a method for structuring endless belts ( 1 ), particularly steel belts, for presses, e.g. double belt presses. According to the invention, a coating is applied to an outer surface of the belt after which metal is removed from and/or applied to the belt. The coating is formed by individual drops, which are projected against the outer surface of the belt and remain thereupon and/or, as done in the prior art, a surface-covering coating is applied, which is degraded and/or removed, e.g. oxidized, in a preferably point-by-point manner by the action of thermally active beams, particularly laser beams, whereupon metal is removed from and/or applied to the uncoated area

[0001] The invention relates to a process for the structuring of endlessbands, in particular steel bands, for presses, e.g. double band presses.

[0002] Presses have a multi-faceted objective. Specifically, adensification of products, in given cases with the application of heator cold, and a certain surface structure are supposed to be achieved.For this purpose, presses of different construction can be used. Inorder to carry out the continuous production of goods such as, e.g.particle boards, decorative plates, or the like, presses with endlessbands, in particular double band presses, are used. In these presses theproduct is not only formed by the surface of the band but alsosimultaneously conveyed by the device, where the action of heat or coldcan take place simultaneously, according to whether there arethermosetting or thermoplastic plastic layers or binding agents.Particularly high demands are made on the constitution of the worksurface of bands of this type. If plane surfaces are to be obtained,then bands of this type are processed mechanically to form a highsurface quality and then, in given cases, provided with a chromiumlayer.

[0003] If it is intended to achieve a certain structuring, indented orraised, e.g. in the form of a wood grain or cork, of the surface, thenvarious processes are known. Thus, for example, it is possible to applyto the surface uniform layer of a radiation cross-linking material, forexample, with slightly cross-linked plastic which through the action ofUV radiation, but also light, in particular blue light, cross-linksfurther and thus becomes insoluble for certain solvents such as water.After illumination of the surface the non-illuminated plastic can bewashed off and subsequently either an etching or also an application ofmetal, e.g. copper, can be carried out.

[0004] An additional, widely used process for the application ofprotective layers which are supposed to prevent either the removal ofthe metallic surfaces or a deposition of metals consists of eitheracid-resistant or acid-sensitive coatings being applied to endless bandsof this type via rubber-elastic rollers, e.g. of silicone rubber, sothat thereafter the removal of the metal, or the coating with a metal,can be carried out. It is disadvantageous in this process that thepatterns of the structuring can only be applied with an original size.Bands with a length of, for example, 40 m can, for example, have 20structures. The band lengths have, however, different lengths dependingon the machine, and depending on themselves for the same machine, sothat, in given cases, an area on the band remains free of thestructures. In order to structure this area as well, it is developed asan extension of a structure by the artistically talented in order tobridge the empty space. Manual compensation of this type has theconsequence that for a plurality of patterns at least one pattern isarranged differently, even if slightly differently, on the steel band sothat, e. g. in the production of decorative plates with a structuredsurface, for example, each twentieth decorative plate is different fromthe other nineteen, or all twenty patterns must be adapted by hand.

[0005] For the present invention the goal is set of providing a processfor the structuring of endless bands in which there is identicalrepresentation on the band of all the patterns with the complete contentof the image, without regard to the length, and, in given cases, thewidth, of the same and wherein undesired spaces can be avoided. Theproducts, which are produced with bands according to the processaccording to the invention, can be completely identical so thatadditional material losses no longer occur and also expensive manualadaptation no longer has to be carried out.

[0006] The process according to the invention for the structuring ofendless bands, in particular steel bands, for presses, e.g. double bandpresses, wherein a coating is applied to the outer surface of the bandand then metal is removed from the band and/or applied to it consistsessentially of a coating being formed by individual drops which areprojected against the outer surface of the band and remain on it and/or,as is known per se, a full-surface coating being applied which,preferably point wise, is decomposed and/or removed, e.g. oxidized, bythe action of thermally acting radiation, in particular laser radiation,after which metal is removed from and/or applied to the uncoated areas.By the application or the removal of the coating with individual drops,or at individual points, an enlargement or reduction of the image to beformed can be carried out in the simplest manner since only the numberand/or drop size [sic] or points, which are kept particularly small,is/are determinative for the possible precise enlargement or reduction.Furthermore, there is the possibility of regulating the spacing of thedrops relative to one another so that a completely desired, precisefilling of the endless band is possible. Due to the fact that the dropsor points are projected against the outer surface of the band,therefore, for example, thrown, a desired, as precise as possible,positioning of the individual drops or points is made possible, e.g. viarollers or the like, which is not changed, in particular in itslongitudinal or axial extension, by the transfer of the image to beformed. With the point wise removal, which is accomplished by thermalaction, of an initially full-surface coating, which is, for example,acid-resistant or solvent-resistant, the desired structures can beextended or shrunken and then the metal surfaces which are exposed, inparticular in the form of a point, are partially removed or coated withmetal. Thermally acting radiation is understood to mean IR radiation,laser radiation, microwaves, or the like. Through the metallic change,specifically removal of the metal or the application of the metal, onthe uncoated areas, the structuring can be carried out by processes,which are already established in technology.

[0007] If the individual drops strike the band essentiallysimultaneously from a plurality of openings, then particularly smalldrops can be projected onto the band, where the speed of the coatingprocess does not have to be affected.

[0008] If, during the coating of the band, there is a movement of theband and openings relative to one another in the longitudinal ortransverse direction of the band, then it is not required that the bandfirst be provided with a layer which, for example, is sensitive toradiation and that an illumination of the coated areas, e.g. accordingto the image, are carried out but rather a quasi-continuous coating ofthe band or continuous removal can be carried out.

[0009] If, during the action of the thermally acting radiation, there isa movement of the band and the source of the thermally acting radiationsource relative to one another in the longitudinal or transversedirection of the band, then a completely exact representation can beachieved via the control of the relative speed, where, by changing thesame, an adaptation in accordance with the length or width of thestructures to be represented can also be achieved in the simplestmanner.

[0010] If the coating of the metallic surface of the band is donedirectly on the metallic surface, then a particularly simple processresults, wherein by omission of intermediate layers the precision of thecoating can be realized particularly simply.

[0011] If, after the projection of the drops onto the metallic surface,in particular by the action of radiation, the coating is fixed, e.g.polymerized, then the solvent behavior of the layers can be changed tothe extent that subsequent removal or application processes are to berealized particularly simply.

[0012] If, after the fixing of the drops, metal of the band isapplied/removed, then a particularly plane base layer of the structuredendless band can be obtained.

[0013] If, after metal application and/or removal with individual drops,the same band is coated once again and once again metal is removedand/or applied, the different layer thicknesses in the structuring canbe obtained in a particularly simple manner.

[0014] If, after the application or removal of metal, the same band isonce again provided with a full-surface coating which, preferably pointwise, is decomposed and/or removed, e.g. oxidized, by the action ofthermally acting radiation, in particular laser radiation, then astructuring on the band of a different depth can be achieved in aparticularly simple manner.

[0015] From EP 0 492 351 A2, which relates to printing technology, it isa known practice to adapt, in accordance with the length and width,patterns for a stencil for screen printing. Therein a screen, i.e. aloose fabric, e.g. of silk, polyester, or the like, is provided with afilm with light-sensitive material. This layer is then provided by meansof a jet printer according to the image to be represented. This image isadapted with a data processing system to the size of the screen.Thereafter there is illumination whereupon the non-illuminated placescan be dissolved out. With a process of this type it is possible toprepare a multi-colored serigraph since a particularly preciseadaptation of the individual colors is made possible.

[0016] The process according to the invention for representing aplurality of individual identical structures on the endless band, whichare arranged in sequence, consists essentially of the length and/orwidth of the structures being changed in proportion to the total lengthand/or width of all the structures taken together. With a process ofthis type it can be achieved that either there are no spaces between theindividual patterns of an endlessly produced band or there are onlynegligible empty intervals between the individual patterns in order toenable cutting the same to length according to the product desired, forexample, melamine resin decorative plates.

[0017] If the length and/or width of the individual patterns is/aredetermined and recorded, preferably stored, and subsequently the lengthand/or the width of the endless band is/are divided by that of thepattern and then the individual structures are adapted in their lengthand/or width to [sic] an integral multiple of the length and/or thewidth of the band, then

[0018] a particular pattern can be adapted to the dimensions of a bandin a particularly simple manner.

[0019] If, after the application and/or removal of the metal to/from theband and the fixed coating of the band, the band is chrome-plated, inparticular hard chrome-plated, then, as is known per se, a particularlyresistant surface can be achieved which can be responsible for a longservice lifetime.

[0020] In the following the process is explained in more detail with theaid of the drawing and the examples.

[0021] The single figure shows in schematic representation a coatingsystem for an endless band.

[0022] The system for coating represented in the Figure has an endlessband 1 which is deflected, or driven, over rollers 2 and 3. At one endis a coating system, which has a projection head 4 which can be movedalong the spindle 5 by turning the same in the longitudinal direction ofthe spindle. The projection head 4 has a plurality of jets, e.g. onehundred, through which the coated material projects onto the steel band,thus being accelerated.

EXAMPLE 1

[0023] A pattern, according to which the desired structuring is supposedto be performed, is recorded with a scanner, or is already present indigitized form. The pattern is stored in a data processing system'sfixed memory, which then serves to control the projection head. The bandof stainless steel is set in rotation at 24 m per minute. The rotationalspeed of the band is controlled via the number of revolutions per minuteof the drive roller. The band has a marking and the time is determinedwhich is needed for the mark to pass by the sensor once again. When auniform motion has been established, then drop-wise coating from the jethead can begin. The drops are accelerated with a frequency of 10 kHzthrough the one hundred jets in a 40 μl raster onto the band. A head ofthis type is the state of the art and can, for example, be taken from EP0 733 951 A2. After a complete longitudinal row has been applied to theband as coating, the jet head is displaced transversely to thelongitudinal direction of the band and the coating is done again. Thecontrol of the jet head is handled via a data processing system in whichthe image recorded by the scanner is modified, by the formation of aquotient, in its length and, in given cases, in its width in such amanner that there are completely proportional identical images on theband without undesired empty spaces. Then the band of austenitic steelwith % by weight Carbon 0.1 Chromium 17.1 Nickel 7.2 Remainder iron

[0024] was etched with an acidic etching bath with FeCl₃. Thereafter thecoating was removed with an organic solvent from the surface of the bandand an additional coating in the form of points, as already described,was applied and etched once again. This process was repeated three timesso that there were three different etching depths. Through the etchingprocess a continuous transition between the individual etchings isbrought about.

[0025] The endless band obtained has 20 identical structures, wherethere are no undesired intermediate spaces.

EXAMPLE 2

[0026] In accordance with Example 1, a band, which was provided over itsentire surface with an unsaturated polyester resin coating, which washardened with UV radiation and has a thickness of 100 μm, was mounted inthe system according to the drawing. The projection head was formed byan Nd-Yag laser with 800 Watt input power. The frequency of the laserpulse was 10 kHz.

[0027] The coating was decomposed with a point size with a diameter of60μ, where a raster of 40μ was maintained. Then a deposition of copperwith a layer thickness of 9 μm was performed, the coating dissolved withan organic solvent, a full-surface coating applied once again to theband in the device of the figure in a spray head running transverselyover the entire width with a blade disposed behind it in thelongitudinal direction and once again decomposed point wise, andsubsequently copper was deposited. This process was repeated threetimes. The band thus obtained was, as known per se, hard chrome-platedand has twenty structures which had no undesired intermediate spaces sothat there were twenty completely identical structures on the band, andthus on the product produced.

[0028] The adaptation to the band can be done not only in thelongitudinal direction but also in the transverse direction. Thedifferent lengths and widths can be obtained not only via the dataprocessing system but also via a change of the rotational speed of theband and the size of the increments of the transverse movement of theprojection head.

1. Process for the structuring of endless bands, in particular steelbands, for presses, e.g. double band presses, wherein a coating isapplied to the outer surface of the band and then metal is removed fromthe band and/or applied to it, characterized by the fact that thecoating is formed by individual drops which are projected against theouter surface of the band and remain on it and/or, as is known per se, afull-surface coating is applied which, preferably point wise, isdecomposed and/or removed, e.g. oxidized, by the action of thermallyacting radiation, in particular laser radiation, after which metal isremoved from and/or applied to the uncoated areas.
 2. Process accordingto claim 1, characterized by the fact that the individual drops strikethe band essentially simultaneously from a plurality of openings. 3.Process according to claim 1 or 2, characterized by the fact that,during the coating of the band, there is a movement of the band andopenings relative to one another in the longitudinal or transversedirection of the band.
 4. Process according to claim 1, characterized bythe fact that, during the action of the thermally acting radiation,there is a movement of the band and the source of the thermally actingradiation source relative to one another in the longitudinal ortransverse direction of the band.
 5. Process according to one of theclaims 1 to 4, characterized by the fact that the coating is carried outdirectly on the metallic surface of the band.
 6. Process according toone of the claims 1 to 5, characterized by the fact that, after theprojection of the drops onto the metallic surface, in particular by theaction of radiation, the coating is fixed, e.g. polymerized.
 7. Processaccording to one of the claims 1 to 6, characterized by the fact that,after the fixing of the drops, metal is applied/removed to/from thecoated band.
 8. Process according to one of the claims 1 to 7,characterized by the fact that, after application and/or removal ofmetal, the same band is coated once again with individual drops, afterwhich metal is once again removed and/or applied.
 9. Process accordingto one of the claims 1 to 8, characterized by the fact that, after theapplication or removal of metal, the same band is once again providedwith a full-surface coating which, preferably point wise, is removedand/or applied, e.g. oxidized, by the action of thermally actingradiation, in particular laser radiation.
 10. Process in particularaccording to one of the claims 1 to 9, wherein a plurality of individualidentical structures on the endless band is arranged in sequence,characterized by the fact that the length and/or width of the structuresis/are changed in proportion to the total length and/or width of all thestructures on the band taken together.
 11. Process according to claim10, characterized by the fact that the length and/or width of theendless bands is/are determined and recorded, preferably stored, anddivided by the length and/or width of the individual structures andsubsequently the length and/or the width of the individual structuresis/are adapted to an integral fraction of the length and/or the width ofthe band.
 12. Process according to one of the claims 1 to 11,characterized by the fact that, after the application and/or removal ofthe metal to/from the band and the fixed coating of the band, the bandis chrome-plated, in particular hard chrome-plated.